PITTSBURGH – The head of Pennsylvania’s Department of Health said Wednesday that its experts are responding to health complaints related to natural gas drilling, but there is no quick and easy way to answer questions about the issue.

Health Secretary Michael Wolf told The Associated Press that the department is working to do research with other public and private partners, such as hospitals.

But in the interview Wolf said he hasn’t spoken directly to Gov. Tom Corbett about possible health impacts from the drilling boom, only to Corbett’s staff, and that the department didn’t ask the legislature for additional money this year to study the issue, which critics have called for.

Wolf’s predecessor, Dr. Eli Avila, said last week that the state has failed to seriously study the potential health impacts of drilling. Avila and other experts said Pennsylvania needs to fund and create a statewide health registry to study the issue.

In 2011, the state House approved $2 million to start one, but Senate GOP leaders and the governor’s office cut the funding at the last minute.

Wolf said that creating a state-funded health registry isn’t the only solution to answering the public’s questions, but the department hasn’t ruled it out.

“People want a quick answer, and unfortunately, on issues like this, there is no quick answer,” Wolf said. “We will absolutely continue to follow up” on complaints that people make.

The Marcellus Shale drilling boom that began in Pennsylvania around 2008 has generated tens of thousands of direct jobs and more than $1 billion in royalties to landowners but also complaints about air and water pollution and the industrialization of nearby communities. The Marcellus Shale also lies under large parts of West Virginia, Ohio and New York.

Some people have complained that nearby drilling led to headaches, nosebleeds and other problems, and there are long-term concerns about the toxic chemicals used in the fracking process that breaks the rock to free gas. But without coordinated statewide research, it’s impossible to know how widespread or dangerous the problems are or even whether drilling is responsible.

Wolf said that state experts have yet to see large-scale health impacts or clusters of people whose symptoms can be linked to shale drilling.

On Tuesday, six of Pennsylvania’s leading environmental groups called for an investigation into how the Department of Health is handling drilling complaints.

“If there is any question that the actions of drillers are causing harm to our air, water and land as well as the health of our citizens, the governor and state agencies must address those concerns immediately,” said a statement from the leaders of PennFuture, the Clean Air Council, PennEnvironment, and the state chapters of the Sierra Club and Clean Water Action.

Patrick Creighton, a spokesman for the Marcellus Shale Coalition, the largest regional industry group, said in an email last week that public health and safety are priorities for the industry.

“There is no higher industry priority than the health and safety (of) our employees, contractors and the communities where we operate,” Creighton said.